would this work to keep online accounts from being hacked

[superduh]

has this been tried.
keep in mind i am not a technical person at all.
also, i'm just guessing and not sure if it has been discussed before.
would it be possible for an "online" wallet to do this

when you create an account-
it will give you a full key (public and private)

you must write down the last 4 of your public key and the last 4 of your private key.
a lot like the modern day pin
then the site DELETES (using industry standards) the last 4 of those account numbers
then when you login in order to send anything you would need to input the 4/4 digits that the site will add
and use to authenticate. that way there will never be a brute force way of sending out any bitcoins unless one knows the digits to the addresses.

does that even make sense

[A Meteorite]

The simple answer is no. Public key cryptography does not work that way. Even if it did, your four digits never change, so a man-in-the-middle attack is all that is needed.

What would work is users generating their own key pair and giving the site their public key. Users would then have to sign something the site gives them with their private key.